Axicon profile metrology using contact stylus method

Abstract

Axicon lenses, characterised by their cone shape, have rotational symmetry. The generatrix of axicons is the surface profile going across the apex of the axicon and the cone angle of the axicon can be calculated from the generatrix. Axicons, widely used in optical alignment and Bessel-Gauss beam generation, require high accuracy in surface and cone angle metrology. However, current methods focus on measuring the cone angle with a stylus profiler, a process in which misalignment and displacement are common when measuring the generatrix. A method is proposed that multiple parallel measurement paths near the apex of the axicon will obtain the generatrix with the specific algorithm. In experiments, the axicon with a cone angle of about 90° was measured by the stylus profiler method (Taylor-Hobson PGI 3D) in the 0.5 mm, 0.4 mm and 0.3 mm distances, whose results show good agreement in the cone angle range and generatrix error. Experimental results prove the feasibility of the proposed method.